Production of resins from coke



Nv.zo,1945. J. H. WELLSETAL 2,389,510

PRODUCTION OF RESINS FROM COKE OVEN GAS Filed Oct. 27, 1943 Pnenied Nov. 2o, 1945 PRODUCTION F RESINS FROM COKE OVEN GAS Joseph H. Wells and Philip J. Wilson, Jr., Pittsburgh, Pa., assig'nors to Carnegie-Illinois Steel Corporation, a corporation of New Jersey Application October 27, 1943, Serial No. 507,886

2 Claims.

In the removal of the light oil from coke oven gas the gas is washed with a petroleum oi-l, commonly termed wash oil. The light oil is then removed in turn from the solvent by distilling the oil solution at temperatures around 100 C. or above with direct steam. 'I'he constituents of the light oil, benzene, toluene, xylene, and the like, boil at temperatures below 200 C., and come oil as distillate. 'I'he Wash oil boils between 250 and 400 C., and remains in the stili.

The distilled Wash oil is returned to the scrubbers and the cycle goes on with continuous circulation of the wash oil.

In addition to the light oil, the wash oil takes up from the gas other constituents, both gaseous and small particles of entrained liquids or solids. A large proportion of this material consists of unsaturated compounds. They polymerize and combine in complex reactions with each other under the elevated temperatures prevailing in the stills, for instance. Some of the new products and the substances washed from the gas are suspended as timely-divided particles in the oil, others are apparently dissolved. Because they distill at rela` tively high temperatures they do not come over with the light oil, but gradually accumulate in the wash oil. With continuous recirculation of the oil the compounds coalesce, precipitate, emulsify with Water and dirt, and otherwise separate from the oil as a brown muck.

This muck separates in all parts of the system. On the scrubber packing it accumulates in masses which plug the gas passages, restrict the flow of gas, and reduce the eiciency of light oil absorption. In the decanters the muck forms a layer between the upper layer of oil and the lower layer of condensed steam and reduces the useful volume of the decanter. In the heat exl changers the muck is deposited on tubes and interferes with heat transfer. In extreme cases the muck, oil, and Water have become completely emulsilled, and the entire system has been shut down until the" emulsion was broken. From time 1 to time muck deposits must be removed from the wash oil system and disposed of.

'Ihe nature ofthe muck from different parts of the system will vary greatly; some deposits are removed as a thin, watery liquid, others as hard lumps. They consist ofintimate mixtures or emulsions of the complex compounds, Water, and some wash oil. Small amounts of dirt which enter the systems, as rust from the apparatus. and dirt which blows into open tanks, also enter the muck.

Accumulations of muck are removed periodically from the diierent points of the wash oil system. The muck is then usually boiled with steam, either direct, in coils, or both, to separate and recover as much oil as possible, and to reduce the volume by eliminating some water.

` If the muck is iinally disposed of by putting on a dump, the high content of organic matter renders it a fire hazard. Burning is difficult on to operate is 250 C. (482 FJ.

account of its water content and the variation in consistency of the material. If burners are used, they plug frequently, but if the heavier material is charged on a grate, it softens and runs through. The muck represents a waste for which no satisfactory means of disposal has so far been found.

We have discovered a method for separating from the wash oil the complex compounds which cause muck formation. By our process these compounds are separated as a resin with characteristics similar to thoseof other resins now utilized in industrial processes. Our process conssts in distilling the wash oil at temperatures higher than those prevailing in the light oil stripping stills, but not so high that the character of the resin is injured. In this distillation the wash oil must be separated in the distillate completely, While the resin is left in the still kettle as a liquid. On cooling to atmospheric temperature it hardens to a clear, red, brittle solid. By control of the distillation conditions resins with different melting points'can be produced. Many of their prop- 'erties are similar to those of synthetic, indenecoumarone resins.

The temperature below which it is necessary Below 250 C. polymerization of the compounds from the gas proceeds properly to produce the resin, and no harmful decomposition will occur.

The apparatus which we prefer to use for this purpose is a vacuum still operated at pressures up to 5 cm. mercury absolute. Higher absolute pres sures can be used, but the separation of the wash oil may be less complete. When. a batch of wash oil is distilled under high Vacuum with proper temperature control the point at which the Wash oil has completely distilled over is readily seen by the drop in the volume of distillate. On further distillation or with increase in temperature some of the resin will decompose and will come over.

An arrangement of apparatus which is suitable for this purpose is shown in the accompanying drawing, the parts being indicated by self-explanatory legends, so specic reference thereto is here unnecessary. In this sketch gas is the source of heat, but the still temperature is con- In some cases the vacuum may be reduced by v the use of direct steam in the still. In U. S. Pat; ent 2,196,878 is describedva still which may prove to be a satisfactory type for this purpose. However, when steam is used it is more diilicult to secure complete separation of wash oil from resin. In addition, unless condensed steam is completely boiled oil?, the nal resin will be Wet and of less value. v

The still described in U. S. Patent 2,196,878 has been developed for the purification of Wash oil by steam distillation, and is used in a number of plants for this purpose. With this still it has proved dimcult 'rf not imposssible to secure a good resin, free from Wash oil. The' residues from. these stills have, so far as we know, been discarded with largeproportions of wash oli. By

the process we have discovered it is possible to take the residue from this still and prepare a resin satisfactory for commercial use. Our process is thus susceptible of operation in two stages; the first, the type of still such as is described in U. S. Patent 2,196,878, removes the bulk of the wash oil; and the preparation of the resin is completed by our process.

vlt'arample.ll batch distillation was made on wash oil withdrawn from the circulating tanks o! a coke plant. The wash oil had been vin use -for a long time and a. large volume of muck was formed regularly in the circulating system. Ihe still consisted of a.kettle with no fractionating column but with a condenser, receiver, 'and a temperature maintained by means o! an oil bath which was heated by a gas burner. Distillation was started with an oil bath temperature of 195 C., and ended at the maximum oil bath temperature of 250 C. with the wash oil all removed. The pressure in the stili throughout the distillation was 1 cm. mercury absolute. .The distillate was a clear, yellow oil and amounted to 80 per cent by volume of the original oil. It was much superior in its properties to the used wash oil charged to the still, but was similar to new wash oil.

The residue in the still was a liquid. On running into a pan it hardened to a clear, dark-red resin. This had a melting point of 92 C., a specie gravity of 1.10, and an ash content of 0.009 per cent by weight.

We claim:

.1. A method of treating used coke-oven gas petroleum wash oil in order to produce a more readilyremovable resin, comprising distilling it at temperatures of from 200 to 250 C. under a vacuum lat pressures up to 5 cm. mercury absolute in the substantial absence of steam causing it and any light oil it contains to be distilled off while leaving a residue of liquid resin comprising the compounds it contains normally forming muck in the wash oil system.

2. A method of treating used coke-oven gaaf petroleum Wash oil in order to produce a more it and any light oil it contains to be distilled oil while leaving a residue of liquid resin compris,- ing the compounds it contains normally forming muck in the wash oil system. the distillation being stopped upon a noticeable drop in the volume of the distillate to prevent decomposition and vacuum pump. The kettle was heated, and the distillationi' the residue..

JOSEPH H. WELLS. PHILIP J. WILSON, JR. 

